As a general rule, use the preposition including when you need a preposition that means (according to wiktionary) “Such as, among which; introducing one or more parts of the group or topic just mentioned. [Eg] ...fill in the details, including your name and address...”. (See Edit 1, below.)
Also as a general rule, use the verb include when you need a verb that means (again according to wiktionary) “To contain, as parts of a whole. [Eg] The vacation package includes car rental” or a verb that means “To bring into a group, class, set, or total as a (new) part or member.” Examples of that last usage with the simple present and with the present participle include
• Does the total include the rental fee?
• Are you including the rental fee in the total?
Regarding the examples in the question, the following forms are correct. (The “is including” forms are clumsy and unlikely to be used by native speakers, but are not incorrect.)
• Most Thais, including me, like spicy food.
• Many Asians, including Thais, like to learn English.
• The price is including free-flow water.
• The price includes free-flow water.
• This book includes a free CD.
• This book is including a free CD.
Edit 1: As Barrie noted, including is not a preposition. Typically it serves as a present participle. See the following extract from OED1 (1901) for some examples of use.
Including ppl. a. [f. INCLUDE v. + -ING.]
1. That includes, shuts in, encloses, or comprises.
1670 G. H. Hist. Cardinals iii. iii. 329 If the Head of the including Faction, offers the Head of the Excluding Party, to assist him at any time, in the Election of one of the Excludents. 1843 MANNING Serm. (1848) I. xiv. 197 God has given him a moral sight to discern the right as the test, and as the including form of true expediency. 1899 Edin. Rev. Apr. 318 The including shafts were masked by ‘pans’ or depressions.
2. Including pres. pple. often governs a sb. particularizing a person or thing included in a group previously (or afterwards) mentioned; = Inclusive of.
Syntactically, it may sometimes be viewed as agreeing
with the word for the group, e. g. ‘I met a large party including your brothers’; but often it appears to agree with an indefinite pronoun one, we, you e. g. ‘including [ = if we, one, you include] servants, the party will number fourteen’. In the latter construction we have a kind of active of the passive absolute clause ‘servants being included’, or ‘if servants are included’.
1853 RUSKIN Stones Ven. II. vi, A large body of English
landscapists come into this class, including most clever
sketchers from nature. 1864 Daily Tel. 20 Sept., These
premises . . were . . in the occupation of several other warehousemen, including Mr. T. Tapling.
